The administration of granulocyte-monocyte colony-stimulating factor (GM-CSF) was associated with complete clinical and haematological response in an adult patient with minimally differentiated acute myeloid leukaemia who presented with pneumonia and moderate neutropenia, but no blast cells in the peripheral blood. The response lasted 9 months. At relapse, a second GM-CSF course resulted in a very good partial remission lasting 5 months, although differences in the kinetics of haemoglobin, neutrophil and platelet recovery were noted. Subsequent recurrences were managed with chemotherapy, a complete remission being obtained twice more and lastly consolidated with myeloablative chemo-radiotherapy supported by a peripheral blood stem cell autograft. This report suggests that GM-CSF should be further investigated as a therapeutic agent in selected cases of AML.